Suction cup for up to 12mm. Aquarium suction cups. For aquarium airline uses, these are the perfect item to attach air lines to your aquarium in an unobtrusive manner. Strong suction power to attach to your aquarium glass. Enable you to hide airlines etc. with ease. Suitable for most of places with smooth surfaces. Suction pad circumference is 30 or 45mm. Extensive application as long as you choose the right size. This will firmly hold the airline in place underwater making the aquarium look much more secure, as well as neat & tidier.